Preparation of phenylene diacetonitrile

ABSTRACT

Novel polyamides are prepared by reacting a dicarboxylic acid with 1,4-cyclohexane-bis( Beta -ethylamine). Unique properties are obtained where the dicarboxylic acid is 1,4-cyclohexane diacetic acid.

United States Patent 1191 Bouboulis Nov. 4, 1975 PREPARATION OFPHENYLENE 2,324,936 7/1943 Kroeper et a1 260/78 R DIACETONITRILE3,012,994 12/1961 Bell et a1 260/78 R [75] Inventor Constantine JBouboulis Union 3,631,201 12/ I971 Farrissey, Jr. et a]. 260/465 NJ.FOREIGN PATENTS OR APPLICATIONS 924,240 2/1955 Germany 260/78 [73]Asslgnee' g fgg fi Engmeermg 925,496 3/1955 Germany 260/78 [22] Filed:Feb. 12, 1971 F I d E Z J Z: 877 879 me man eta., em., 0. [21] Appl.No.: 115,140 (1960). g pp Related US. Application Data 63 c r r f s N718,934, A '1 4, 1968, Prlmm Examiner-Law's Gotts 1 $2,1 2,12 0 er 0 p"Assistant Examiner-Dolph H. Torrence [g2] U.S.3l. 260/465 H; 260/78 R[57] ABSTRACT 1] Int. l C07c 12/66; C08g 20/20 Novel polyamides areprepared by reactmg a (bear- [58] Fleld of Search 260/465 H boxylic acidwith l,4 cyclohexane bis(fiethylamine) Unique properties are obtainedwhere the dicarboxylic [56] UNITE r S ::rENTS acid is 1,4-cycl0hexanediacetic acid.

9/1938 Carothers 260/78 R 2 Claims, No Drawings PREPARATION OF PHENYLENEDIACETONITRILE BACKGROUND OF INVENTION It is well known to preparepolyamides of bifunctional carboxy compounds and diamines. Polyamidesare advantageously employed in the manufacture of tibers, yarns,fabrics, film, extruded products, coating compositions, electricalinsulations, molding compositions, etc.

For a number of years a polyamide, commonly known as Nylon 66, derivedfrom the condensation of adipic acid and hexamethylene diamine hasenjoyed commercial success because of its excellant properties. Nylon 6,a closely related polyamide is derived from the self-condensation ofepsilon-caprolactam. 1,4- cyclohexane-bis(methylamine) has beenincorporated in nylon 6 type polyamides as a modifier; see for example,US. Pat. No. 2,985,627, incorporated herein by reference.

High melting polyamides have been prepared from essentially trans1,4-cyclohexane-bis(methylamine). As the percentage of cis isomerincreases, the melting point decreases; see for example, US. Pat. No.3,012,994, incorporated herein by reference.

It is well known that as the length of the diamine molecule increases,the melting point of the polymer decreases. Available prior art datawould lead to the prediction that for a given diacid an increase in thelength of the diamine chain by two methylene groups should result inabout a 20C. decrease in melting point of the resulting polyamide.

SUMMARY OF THE INVENTION It has now been found that polyamides formedfrom 1,4-cyclohexane-bis(B-ethylamine) have melting points about 10C.above the analogous polyamides formed from 1,4-cyclohexane bis(methylamine) [CBM], a homologue of 1,4-cyclohexane-bis(B-ethylamine)[CBE] containing two less methylene groups. Furthermore, the polyamidesof this invention have improved properties over CBM polyamides or nylon66.

It has been found that CBE/adipic acid (CHE-6 polyamide has highercrystallinity and lower moisture absorption than the anologous CBM-6polyamide. Additionally, it has a higher elastic modulus and elongationthan nylon 6,6. In general, CBE-6 polyamide combines the best propertiesof both CBM-6 and nylon 6,6 polyamides. Its excellent dimensionalstability makes it especially well suited for molded articles inaddition to tire cord, fibers, etc.

DETAILED DESCRIPTION This invention relates to a novel polyamide derivedfrom a dicarboxylic acid and l,4-cyclohexane-bis(,8- ethylamine) and aprocess for preparing said amine.

The diamine itself, 1,4-cyclohexane-bis(,B-ethylamine) hereinafterreferred to as CBE, is well known to the art and is not claimed to benovel per se. Its use to form polyamides with surprising properties is,however, novel. Processes for preparing amines are well known to theart.

Aromatic alkyl monoamines have been prepared from aromatic nitriles byhydrogenation of the nitrile in 2 the presence of a Raney catalyst suchas Raney Nickel or Raney Cobalt, see for example US. Pat. No. 2,953,490,incorporated herein by reference. Aromatic alkyl amines have beenconverted to cycloalkyl amines by hydrogenation of the ring in thepresence of ruthenium dioxide as the catalyst, see for example US. Pat.

- No. 3,014,966 incorporated herein by reference.

A particularly advantageous method of producing1,4-cyclohexane-bis(B-ethylamine) [CBE] is by the reaction ofpara-xylylene chloride with sodium cyanide to form para-phenyleneacetonitrile and thereafter hydrogenating the compound.

The prior art teaches the preparation of para-phenylene acetonitrilefrom para-xylylene bromide and potassium cyanide using water and ethanol(ca. 1:3 vol. ratio) as the solvent, see for example Conditions ofFormation of Rings Attached to 0-, m-, p-positions of the BenzeneNucleus, A. F. Titley, J. Chem. Soc., 1926, 508, which is incorporatedherein by reference. Though the prior art method claims a yield of aboutthis yield is based on the raw product which is a dirty brown inappearance and requires purification by recrystallization. Furthermore,the raw product must be recovered from the reaction system by extractionwith ether. Substitution of para-xylylene chloride for the bromide andsodium cyanide for the potassium salt gives essentially the same result.

Surprisingly, however, by judicially selecting the solvent medium, theyield is increased to but more important, the product is recovereddirectly by filtration and requires no further purification. Hence, notonly is yield increased, but the product is of a higher quality andrecovery costs are reduced (i.e. extraction vs. filtration).

It has been found that a particularly advantageous solvent system isdimethyl formamide (DMF) and water. The DMFIH O volume ratio may varybetween about 2:1 to about 1:15; preferably, the ratio is between about2 to 1 to about 1 to 1 more preferably about 1.8 to 1 to about 1.3 to l.

The reaction is carried out by dissolving the sodium cyanide in thewater and slowly adding the para-xylylene chloride dissolved in the DMFto the cyanide solution. There generally is an initial induction periodbefore reaction occurs; thereafter, the reaction is exothermic. It isadvantageous to cool the reaction mixture. More preferably, thepara-xylylene chloride is added at such a rate that the temperature ofthe system is maintained at 60-65C. A water-dimethyl formamide mixturemay be used as the solvent for the cyanide salt. It is particularlyadvantageous to incorporate about 10 to about 25 volume of the DMF inthe water-cyanide solution.

After completion of para-xylylene chloride addition the temperature ismaintained, by heating, at about 60 to about 65C. for about 15 minutesto about 1 hour. The product is then precipitated by the addition ofabout one to about 4 volumes of water based on the total reactantsolution volume. Recovery of product, para-phenylene acetonitrile, is byfiltration.

The para-phenylene acetonitrile may then be hydrogenated to form1,4-cyclohexane-bis (B-ethylamine). It is necessary to hydrogenate thenitrile to the amine first in the presence of a Raney catalyst such asRaney Nickel or Raney Cobalt. Preferably, the catalyst is Raney Cobalt.Hydrogenation of the aromatic ring is accomplished by using a rutheniumoxide catalyst. The hydrogenation of the nitrile group cannot beaffected 3 by this catalyst. Not wishing to be bound by the theory it isthought that the nitrile group either poisons the ruthenium oxidecatalyst or deactivates the aromatic ring. Conditions for thesehydrogenation reactions and preparation of the catalysts are well knownto the art.

In the preparation of the polyamide, the 1,4- cyclohexanebis(B-ethylamine) is reacted with a dicarboxylic acid. The metehod ofpreparation is well known to the art. Ordinarily, a salt of the acid isprepared by reacting with the amine, the salt then being heated to driveoff water, thereby forming the polyamide. Alternately, it is sometimesadvantageous to use a spinerette technique to form fibers of thepolyamide by reacting in solution, the amines with the diacid chloriderather than the acid. In this the polyamide is formed, directly, into afiber suitable for use in the making of synthetic woven fabrics.

Any dicarboxylic acid may be used to form the polyamides of thisinvention. Carothers et al., have generally disclosed a wide range ofdicarboxylic acids suitable for use in the preparation of polyamides,see for example US. Pat. No. 2,163,584 incorporated herein by reference.These acids may be represented by the I general formula:

l-IOOCCH RCH COOH where R is defined as above. Particularly,advantageous fiber forming polyamides are prepared when R is (CH whereinn is an integer of 2 to 8.

It is obvious to one skilled in the art that mixtures of the aforesaidacids may be used, resulting in the corresponding structures of mixedacids.

Of particular interest is 1,4-cyclohexane diacetic acid. This acid hasbeen found to give surprising and unique results.

Conventional polyamides, i.e. nylon 6, 6 and nylon 6, lack highrigidity. This deficiency has prevented their wide use as engineeringplastics or for crease resistant fibers.

It is known that one can synthesize high modulus (high rigidity)polyamides from commercially available diamines by utilizing diacidscontaininig phenylene rings. For example, high modulus polyamides knownto the prior art are the condensation products of hexamethylenediaminewith terephthalic acid and of hexamethylenediamine with 1,4-phenylenediacetic acid. These polymers, however, are not commercially suc- 4cessful due to their excessively high melting points (360 and 300C.respectively). Hence, processing is not practical due to decompositionwhile processing.

Polyamides of a cis-trans mixture of 1,4-cyclohexane dicarboxylic acidgive brittle, thermally unstable polyamides. The cause is thought to bedue to the deleterious effect of the cis isomer.

Surprisingly, however, superpolyamides of mixtures of cis and trans1,4-cyclohexane diacetic acid are prepared with advantageous propertiessuch as high modulus, excellent thermal stability and a reasonablemelting point from the standpoint of processability.

Any diamine may be used to form these polyamides. As indicated byCarothers, supra, the preferred structure of the diamines is wherein Ris a divalent hydrocarbon radical of at least two carbon atoms. Hence, Rmay be:

wherein n is a cardinal number from 2 to 18 and R and R areindependently selected from linear or branched chained alkyleneradicals. Other suitable diamines are those wherein R isp,p'-oxadiphenylene or p,pmethylenediphenylene.

Altemately, R may be a heterogeneous radical wherein R is (C 2)". A am r2)". A A 2)m' wherein m and m are each carbinal numbers of about 2 toabout 5 carbon atoms; and A is selected from the group consisting ofoxygen, sulfur and EXAMPLE 1 Seventeen grams of1,4-cyclohexane-bis(B-ethylamine) of approximately cis, 30% trans isomercomposition was dissolved in ml of absolute ethanol. The diamine wasreacted with 14 grams of adipic acid dissolved in 250 ml of absoluteethanol. The precipitated white salt was filtered and air dried.

Five grams of the above salt was placed in a heavy walled tube which wasevacuated, sealed and heated to 215C. for 2 hours. The tube was thenopened and heated for about one-half hour at 28 5C. under nitroofincreasing amine chain length compared with CBE and CBM polyamides.

TABLE I EFFECT OF INCREASING DIAMINE MOLECULE LENGTH ON MELTING POINT OFPOLYAMIDES Melting Point of Polyamide C.

Diamine Adipic Suberic Sebacic H N(CH2)sNl-I 260-263 215-220 209 H N(CH),,NH 235 200-205 197 H NC D-C-Nm 258 237 205 (70% cis, 30% trans) HN-CC-.C -CCNH, Predicted 230 220 Y 195-200 (70% cis, 30% trans) Actual273 244 237 The resulting product was an opaque polyamide having acrystalline melting point of 257-273C. and an inherent viscosity of 2.0(measured at C. from a 0.5% solution of polymer in m-cresol).

EXAMPLE 2 A salt was prepared as in Example 1 usingabout 5 grams of CBE(55% cis 45% trans) in 50 ml ethanol and 4.1 grams of adipic acid in 150ml ethanol. The air dried salt was reacted in a sealed tube at 220C. for2- /2 hours; then under nitrogen at atmospheric pressure for l- /2 hoursat 300C. and finally for one-fourth hour at 2-6 mm Hg pressure at 300C.The resulting polyamide had a melting point of 265302C.

EXAMPLE 3 A solution of 5 g. l,4-cyclohexane-bis(B-ethylamine), composedof 93% cis, 7% trans isomers, in 50 ml of absolute ethanol was mixedwith a solution of 4.1 g. adipic acid in 150 ml. of ethanol. Theresulting salt was dried and heated as in Example 2, except that thefinal temperature cycle was 280C. The polyamide formed had a meltingpoint of l882l4C.

Examples 1-3 show that increasing the percentage of cis isomer resultsin a lowering in melting point. This is consistent with the prior artteachings of U.S. Pat. No. 3,012,994 incorporated herein by reference.It will be noted, however, that the patent, relating tocyclohexane-bis(methylamine) [CMB] polyamides, shows substantially lowermelting points for similar products. For example, a cis, 70% transmixture of CBM reacted with adipic acid melts at 295-303C. (equivalentto 55 cis 45 trans CBE) whereas a 50% cis, 50% trans mixture results inan adipic polyamide which melts at 265273C. (equivalent to 70% cis, 30%trans mixture of Example 1). By contrast, a 75% cis, 25% trans mixtureresults in a polyamide which melts at l85-l92C., a melting point belowthat obtained with a 93% cis, 7% trans CBE/adipic acid polyamide(Example 3). Hence, it is demonstrated that equivalent polyamides formedfrom CBE melt at a higher melting point than CBM polymers. 3

To further illustrate the fact that CBE polymers have a higher meltingpoint and that this is contra to what would be predicted, Table I showsvarious polyamides The comparative data show that CBE polyamides havemelting points between 2540C. higher than their predicted values and atleast 10C. higher than the equivalent CBM polymer. The predicted dataare based on the effect of increasing the diamine chain length by twomethylene groups.

EXAMPLE 4 Polyamides were prepared in the manner of Example 1 usingsuberic and sebacic acids in place of adipic acid. The CBE-suberic acidpolyamide had a melting point of 244C. and an inherent viscosity of 1.5.The CBE-sebacic acid polyamide melted at 237C. and had an inherentviscosity of 1.17.

EXAMPLE 5 A polyamide salt was prepared from 5.00 g. of 1,4- cyclohexanediacetic acid (68% cis, 32% trans) and 4.42 g. of 1,4-cyclohexane-bis(B-ethylamine) (70% cis, 30% trans). Five grams of the salt waspolymerized in the manner of Example '1 first by heating to 230C. for 1hour, then at 280C. for one-half hour undernitrogen and three-fourthhour at 4 mm Hg pressure. The final polyamide was tough and clear with amelt temperature of 2l0-220C.

EXAMILE 6 A solution of 130 grams (2.65 moles) sodium cyanide in 200 mlof water was placed in a four-necked flask, equipped with atherriiowell, mechanical stirrer, electrically heated addition funneland a condenser. A solution of 200 grams 1.15 mole) of p-xylylenechloride in 200 ml of dimethyl-formamide was added drop wise withconstant stirring and such a rate as to maintain the reactiontemperature at 60-65C. The p-xylylene chloride solution was'maintainedat about 60C. to prevent solid precipitation. The reaction wasexothermic and addition took 2 hours. At the completion of the addition,the temperature was maintained by external heating for an additionalhour. The mixture was then poured into 2 liters of water. Theprecipitated solid was filtered and washed with an additional liter ofwater. The product yield was (ca. 152 g.) of paraphenylenediacetonitrile having a melting point of about -97C.

(C., under N 368 370 CBE-6 polyamide shows obvious advantages overnylons 6,6 and 6 in having lower moisture regain, higher tensilestrength, much higher flexural modulus and lower density.

EXAMPLE 7 6-CDA 70% cis, 30% trans) polyamide A solution of 10 grams(.05 mole) 1,4-cyclohexane diacetic acid (CDA) in 200 ml of absoluteethanol was mixed with constant stirring with 6.0 grams (0.052 mole)hexamethylene diamine dissolved in 50 ml of ethanol. the precipitatednylon salt was allowed to stand overnight and then was filtered and airdried. The pH of 1% aqueous solution of this salt was 7.9. g. of thenylon salt was placed in a heavy wall tube which was evacuated,sealedand heated at 218-220C. for 2.5 hours. After the tube was cooled it wasopened and the polymerization continued at 280C. for 50 minutes undernitrogen and for 40 minutes at 0.5 mm Hg. Throughout the under vacuumpolymerization, nitrogen was bubbled into the molten polymer via acapillary. Melting point. of the resultant polyamide 22 l-247C. (DTA).mm 1.34.

p v EXAMPLE 8 S-CDA:(70% cis, 30% trans) polyamide A polyamide salt wasprepared as described in the previous example from 5.00 g. -(0.035 mole)1,8- octanediamine and 6.61 g. (0.033 mole) 1,4-cyclohexane diaceticacid. 5 g. of this salt was placed in a heavy wall tube which wasevacuated, sealed and heated at 220225C. for 2.5 hours. Thepolymerization tube was opened, a capillary, connected with a nitrogensource, was introduced and the tube was heated for 1.5 hours undernitrogen and for 1.25 hours under vacuum. Polyamide mp. 209C. 1 1.40.

EXAMPLE 9 10-CDA (70% cis, 30% trans) polyamide A polyamide salt wasprepared as in Example 7 from 5.00 g. (0.029 mole) 1,10-decanediamineand 5.70 g. (0.028 mole) 1,4-cyclohexane diacetic acid. 5 g. of thissalt was heated in an evacuated and sealed thick wall tube for 2.5 hoursat 220225C. The prepolymer thus prepared was further heated at 280C. for1.5 hours under nitrogen and 1.25 hours under vacuum. Softening point ofthe noncrystalline polyamide, 210C. 17 1.54.

EXAMPLE 10 S-CDA cis, 30% trans) polyamide A polyamide salt was preparedby mixing a solution of 8.40 g. (0.042 mole) 1,4-cyclohexane diaceticacid in 150 ml absolute ethanol with a solution of 4.5 g.

' (0.044 mole) 1,5-pentanediamine in ml ethanol.

The nylon salt which precipitated out was filtered and air dried toconstant weight. 5 g. of this salt was placed in a heavy wall tubesealed and heated for'2.5 hours at 220C. The resultant prepolymer wasfurther heated at 280C. for 1.5 hours under nitrogen and for 1 hourunder vacuum. 1 1.46. Softening Point C.

EXAMPLE 1 l m-Xylylenediamine-CDA (70% cis, 30% trans) Polyamidem-Xylylenediamine 5.0 g. (0.037 mole) and 7.0 g. (0.035 mole) of1,4-cyclohexane diacetic acid were used to prepare a nylon salt in themanner described in previous examples. 5 g. of this salt was heated inan evacuated heavy wall tube at 220C. for 2.5 hours. The prepolymer wasfurther heated at 300C. for 1.5 hours under nitrogen and for 1 hourunder vacuum. MP. 271282C. 17,- 0.47.

Examples 7-1 1 demonstrate that suitable polyamides having meltingpoints within the processing range of these polymers may be prepared.

In order to show the unique advantage of 1,4- cyclohexane diacetic acidpolyamides, a comparison of the physical properties of 6-CDA polyamide(Example 1) nylon 6 and nylon 6,6 is presented in Table II.

TABLE II when prepared with 1,4-cyclohexane diacetic acid have higherrigidity (modulus), greater tensile strength and lower moisture regain.Furthermore, these properties are achieved in a polymer having a meltingpoint similar to those polyamides (nylon 6 and nylon 6,6) commerciallyin use.

Since it will be readily evident to one skilled in the art that manydifferent embodiments may be made without departing from the spirit ofthis invention, it is not intended to limit the scope thereof to theparticular embodiments disclosed herein.

1 claim:

1. A process for preparing para-phenylene diacetonitrile whichcomprises:

a. dissolving sodium cyanide in a first solvent selected I from thegroup consisting of water and a waterdimethylformamide mixture;

b. dissolving para-xylylene chloride in a second solvent consisting ofdimethylformamide, the ratio of 3 ,9 17,665 9 10 Second Solvent to firstsolvent bemg about 2 to 1 to e. separating the para-phenylenediacetonitrile from about 1 to 1.5; c. adding the para-xylylene chloridesolution to the the water-(hmethylt-omamlde Puxture' Sodium cyanideSolution; 2. The process of claim 1 wherein the para-xylyleneprecipitating the para pheny1ene diacetonimle so 5 chloride solution isadded at a rate sufficient to mainformed by adding to the reactantmixture copious tain the reactants at about amounts of water; and

1. A PROCESS FOR PREPARING PARA-PHENYLENE DIACCETONITRILE WHICHCOMPRISES: A. DISSOLVING SODIUM CYANIDE IN A FIRST SOLVENT SELECTED FROMTHE GROUP CONSISTING OF WATER AND A WATER-DIMETHYLFORMAMIDE MIXTURE, B.DISSOLVING PARA-XYLYLENE CHLORIDE IN A SECOND SOLVENT CONSISTING OFDIMETHYLFORMAMIDE, THE RATIO OF SECOND SOLVENT TO FIRST SOLVENT BEINGABOUT 2 TO 1 TO ABOUT 1 TO 1.5, C. ADDING THE PARA-XYLYLENE CHLORIDESOLUTION TO THE SODIUM CYANIDE SOLUTION, D. PRECIPITATING THEPARA-PHENYLENE DIACETONITRILE SO FORMED BY ADDING TO THE REACTANTMIXTURE COPIOUS AMOUNTS OF WATER, AND E. SEPARATING THE PARA-PHENYLENEDIACETONITRILE FROM THE WATER-DIMETHYLFORMAMIDE MIXTURE.
 2. The processof claim 1 wherein the para-xylylene chloride solution is added at arate sufficient to maintain the reactants at about 60*-65*C.